Wal-Mart uses smart coding to make its mobile web site load faster

The average load time for the home page of the mobile commerce site of Wal-Mart Stores Inc. dropped by 540 milliseconds last week, according to the Internet Retailer-exclusive Keynote Mobile Commerce Performance Index for the week ending July 6. It dropped the weight of its home page by 143 kilobytes, and less weight means quicker page loads.

Wal-Mart shed the weight not by reducing the functionality of its home page but rather with a coding method called Data Uniform Resource Identifier (URI), which groups elements of a page and codes them directly into the page’s HTML or CSS file. That way, multiple server requests for various elements are cut down to just one, for the HTML or CSS file.

Wal-Mart uses Data URI for 15 out of its 43 page elements, says Krishna Reddy, mobile performance evangelist at Keynote. “With this approach, Wal-Mart doesn’t require additional HTTP requests to download the static images, thereby saving Wal-Mart the roundtrip time that would have been spent downloading the static resources,” Reddy says. “Using Data URI helps in reducing the total number of HTTP requests, which is the mantra retailers must follow on wireless networks.”

Wal-Mart’s mobile home page loads in 10.03 seconds, down from 10.57 seconds the previous week. Sears, which has held the No. 1 spot for several weeks, only uses six page elements on its mobile home page, which loads in just 2.24 seconds. The average load time for the 30 retailers on the index is 11.74 seconds.

Wal-Mart did not respond to a request to comment on its mobile site performance.

Keynote measures, exclusively for Internet Retailer, 28 standalone m-commerce sites optimized for smartphones and two responsive design sites, which are single sites that render content in ways that fit the screen size of a device, including desktop PCs, tablets, smartphones and smart TVs. For the index, Keynote measures the smartphone versions of the responsive sites.

The 30 representative sites include merchants in multiple categories and channels, and of multiple sizes, ranging from such giants as Amazon.com Inc. to mid-sized retailers like Toolfetch.com LLC. Keynote tests the sites in the index every hour Monday through Sunday from 8:00 a.m. through midnight EDT, emulating the Apple iPhone 5 smartphone on two wireless networks: AT&T and Sprint, both using 3G, 4G and 4G LTE networks. Keynote runs the tests in Dallas, New York and San Francisco.

Keynote combines a site’s load time and success rate, equally weighted, into a single score. Given that both performance and availability are important, the score reflects the overall quality of the home page; a higher score indicates better performance. Scores also reflect how close sites are to each other in overall quality. The index average score is the midpoint among all the sites’ scores. To consistently rank high on the Keynote index, sites must hit availability targets of 99.5% or better and be faster than 10 seconds to load on average. Top-performing sites load in under five seconds.

Today, 20% of U.S. Internet-enabled mobile phone users have 4G or 4G LTE wireless data connections, 71% have 3G, and 9% have 2G, according to research firm Informa Telecoms & Media. And according to research and consulting firm Deloitte, 63% of U.S. smartphone users most often connect to the web on their devices on a Wi-Fi network.